Floating pressure cam



J. E. SHAFER FLOATING PRESSURE CAM April 6, 1948.

Filed Aug. 6, 1945 2 She ets-Sheet ,1

- JuZz'us E.6'kafer gy-2/-/7 F2257;

Patented Apr. 6, 1948 UNITED STATES PATENT OFFICE FLOATING PRESSUREJulius E. Shaier, Chicagqhm...

Application'August '6, 1945; Serial No. static 4 Claims.

The present invention relates. to a floating pressure cam and moreparticularly to a resiliently urged cam follower construction formaintaining accurate riding contact on acam to control: rocking of atoolcarriage of a lathe for turning aecurate profiles or contours. I

There are in use at the present time lathes equipped with double formerbars for controlling transverse or rocking motions of tool carriages onthe lathes, but it has been found that it is difficult to secure extremeaccuracy or adjustment Without unduefriction between the camsand theshoes of the cam followers.

The present invention makes possible the accurate adjustment of cams andcam shoes for assuring positive ridingengagement of the shoes againstcams fixed in one of the former bars by providing a floating pressuremounting for a follower cam in the other former bar.

An object of the present inventionis to provide a floating pressurefollower cam mountingwhich will maintain positive and uniform contact ofa cam shoe with a cam without subjecting the cam to excessive wear.

Another object of the present invention is to provide a novel cam barconstruction fordouble formers wherein different cams may be used in thesame formerbars thus reducing costof special cams to a minimum. i

A further objectof the present invention is to provide a former barconstruction for toclcarriages of lathes wherein cams may be remew ablymounted, accurately adjusted lengthwisoof the bar, and locked inadjusted position to facilitate accuracy of cooperation between the camsand the tool carriageof the lathe.

The invention has for an additional object the provision of means foradjustably mounting a cam in its former bar to secure accuracy ofcooperation between the camand the carriage arm by adjustment of the camlengthwise of its bar.

A further object is toincrease the accuracy of profile turning latheshaving rocking tool or work carrying carriages while decreasing the camsetting time for such lathes.

Another and still further object of the present invention is to providea former bar construction wherein cams used for controllin transverse.car-t riage movementsfor turning one type'of surface or profile may bequickly removed an-d replaced with cams for turning another type ofsurface or profile with minimum lossyof time.

A still further object oi the present invention is to providea doubleicrmer bar; cam'mounting arran ement whereinextremeaccuracy of controlof, transverse earrings movements is achieved,

additional .obiect. of the; present. invention is o pr vide a float ng pssure cam; arran ement for" causing positive engagement of a cam shoe ainstrits cam re ardless. of the. irre ularity f he surtace.

The objects; of the present invention are achieved by the mtqvision.015; a; floating pressure meuhtingrq the cam. in the lower fo mer bar.which bearsaaai st the. camshoes with p essure sufiicienttomaintainpositivecontact of the shoes with the. cam. In: the upper .iormer bar,regardless of its contour without. imnqsing undue friction.- on theshoes; and, cams.

The abo e... other amivfurther objects of t e.

present: inven on w ll eapparent r m th ollow g-r, e r tion and, theaccompan ng. rawings.

An embodimfintof the pliesentinvention is 11-.

lustmted in the, accompanying drawings and the ews ther of are asfollows; Fi u 1 is. a. front. side. elevational view of a lathe having.a. bracket applied thereto and equipped with-former bars. and earns. orthe present invention. showing the relationship of parts with the toolcarriage. part. way along its range of travel.

Fi ure .2. is' an enlarged transverse cross-sectional view taken alongthe. line II-II ofFigure 1 and showing, in end elevation, the toolcarriage of the lathe, the cam shoeson the arm of the carriage, theformer bar carriage, and the cam carrying. former bars with thecarriagearm in horizontal position.

Figure 3 1s a fragmented end elevational view oii'theiree end of thecarriage arm, showing rela-. tive position ofthe cam shoes when the camtilts the arm downwardly.

Figures is a top plan view of the upper former bar.

Figure '5' is a top plan view of the lower former bar.

Figure 6 is an enlarged fragmentary side view,

partly in longitudinal section and partly in elevation, ofthe upper andlower former bars of the present invention showing the bars equippedwith double cams for oscillating the lathe carriage carrying a tool postwith two cutting tools to make two successive cuts including a roughingcut and a. finishing out on the inside faceof a pillow block 4 to therecess. To limit upward movement of th cradle in its recess and to loadthe springs to the desired pressure, bolts 41 and 48 are entered throughbores 49 and 50 in the cradle and are threaded into threaded bores 5|and .52, respectively, in the bar C. The upper ends of the bores 59 and50 are counterbored at 53 and 54 to receive the heads of the bolts 41and 48. Adjustmerit of the bolts 49 and 50 in the cradle, as

in shape, andv has threaded holes l6. extending in from its top surfaceto receive bolts for suspending the bar from the top of the bracket I5.

Substantially midway of its length alnd'o'pening through the undersurface of the bar is a rectangular recess l1 extending part way of theheight of the bar terminating in shoulders Ila. Above the recess the baris provided with an elongated slot l8 having a shouldered margin L9. Therecess I! of the upper former bar 13 affords a space in which cam meansmay be secured. Figure 6 shows two similar cams and 2| having theircam'surfaces 22 of the same contour. Cams 2B and 2| are separated by ashim 23 while a filler block 24 is inserted between the cain 2l and theadjacent end of the recess IT. The cams have threaded bores 25 and 26 toreceive cap screws 21 and 28. The heads 29 and 30 of the screws rest onthe shoulder or ledge l9 and when the screws are tightened into the camsthey hold the cams tightly against the shoulders Ila.

In order to adjust the cams lengthwise of the former bar B the bar has alongitudinal bore 3| extending inwardly from one end thereof to therecess IT. The outer end of the bore 3| is threaded at am. A long bolt32 is seated in the bore 3| to bear against the cam 20 and has a head32a threaded into the threaded bore 3la, to adjust the bolt lengthwiseof the former bar. With this adjustment, and the use of the shim 23 andfiller block 24, it is apparent that thecams may be so positionedlengthwise of the bar as to be accurately adjusted with respect to thefollower shoes on the arm of the carriage. V v

The bar B is provided with transverse apertures 33 through whichsuitable attaching bolts may bepassed to'en'gage the bracket. l5, ifdesired. 1

The lower former bar C is likewise of elongated rectangular formationand is provided near its ends with longitudinally elongated slots 34 and35 through which attaching bolts may be passed to fasten the bar to theframe l5. .The provision of the elongated slots. 34 and 35 is to enableendwise adjustment of the bar with respect to the bracket.

The bar C is formed with an'open topped, closed bottom central recess36, which is rectangular in side elevation and which extends the fullwidth of the bar. A cradle 31 is fitted Within the recess 36. Thiscradle is provided with a ecess 38 in which the lower cam is mounted. hecam 39 is fastened in the recess 38 of the cradle fill by means of capscrews ill entered through openings M in the bottom of the cradle and inthreaded bores 42 in the cam. The cradle is counterbored at 43 toreceive. the heads of the screws. The confronting faces of the bottom ofthe recess 36 of the bar C and of the cradle 37 are provided with aplurality (fourbeing shown) of registering bores 44 and l5 which whentheparts'are assembled .co'nt'ain springs lfi which before stated,adjustably loads the springs 46 and controls the level of the cradlerelative to the bar C. Figure 6 shows two of the four springs 36encircling the bolts 49 and 50.

It will thus be noted that a floating pressure mounting is provided forthe lower cam 39 in the cradle 31.

The contour faces 22 of the upper cams 20 and 2| are convex,consequently the upper face of the lower cam 39 is formed withcomplementary concave faces 55 and 56 in register with the cams 2i] and2|. The'concave cams-55 and 56 are shown as separated by a ridgej5l.

"As shown in Figure 2, the tool carriage I2 is provided with a laterallyprojecting'armiddisposed to travel between the upper and lower formerbars B and C 'inthe bracketl5. 'The outer end of the arm 58 isbifurcated .to pivotally support upper calm shoe 59 and lower cam shoefill. The shoes'are pivoted to the end'of the bar 58'by pins BI and 62,respectively;

It will be noted in Figure 2 that the cam-shoes 59 and 60 are ofappreciable widthto have relatively long lines of sliding contact on thewide confronting faces of the former bars andpams. These long transversecontact linesprevent the shoes from cocking and hold the shoes invertical positions. As the arm '58 oscillates from its lowermost angularposition to its uppermost angular position, the pins 6! and 62 swinginan arc and the shoes will be moved'relatively to each other, slidingback and forth across the faces of the cams but the long contactlines ofengagement with the cams will hold the shoes in true vertical positions.1

The arcuate path of the pivot pins changes the vertical distance betweenthe tilting centers of the shoes, and slightly changes the distancebetween the apices or cam-engaging faces '63 and 64 of the shoes. Thusas shown in Figure-2, the :distance D between the apices of the-shoes isgreater, when the centers of pivots BI 'and 62 are vertically aligned,than the distance D' shown in Figure 3, when the pivot centers are'outiof vertical alignment. -Heretofore it has been necessary to set theriding clearance for the sho'es on the camswhen the pivot centers werein vertical alignment and the distance D was maximum. Such a setting,however, results in 'loosene'ss or play between theshoesand cams whenthe distance D decreases. As aresult, accurate profile cutting was notobtained. In the'present in- Figure 6 shows a sectional view through apil low block work piece II, the interior surface of amazes which is tobegiven a truly spherical-shape by the cutters mounted on the cutterbar;l3. Two cutters 65 and 6B are mounted intandem on the cutter bar I3. The first cutter 65 is to take a rough cut in the work piece II, andthe second cutter 66 is to make a finishing cut, in one advance of thecarriage. V l

The cams 20 and 2| and 39.are designed to oscillate the carriage fortransverse movement thereof in a manner to make the spherical cuts inthe work piece I l as described.

Figure 6 shows the first cutter 65 as having been moved through the workpiece III-and the second cutter 66 in cutting engagement with theinteriorsurface of the same.

Figure 6 shows the cam shoes 59 and 60 against the high side ofconvexity of the first cam 2| and the low point of concavity of thelower cam 56 of the cam member 39.

It is to be understood that when the parts are arranged to begin initialmovement of the carriage to the left, as viewed in Figures 1 and 6, theapices of the cam shoes will be at the extreme right (Figure 6) of thecams. As the carriage is advanced to the left, the shoes will movedownwardly under the convexity of the face of the first cam 2! thusmoving the first cutter 65 inwardly of the work piece to its maximuminward movement as determined by the high point of the cam 21. Thecarriage will then swing back as the shoes move into register with theshim 23 at which time the first cutter 65 is freed of engagement withthe work piece and the second cutter is about to begin its operation.Continuation of the movement of the carriage to the left will cause thecam shoe to engage the second cam 20 and oscillate the carriage in amanner to direct the second cutter 66 alon spherical lines to finish thesurface of the work piece. When the carriage has reached its limit ofmovement to the left, mechanism (not shown) but well understood, becomeseffective to shift the cutters away from the work piece and enablewithdrawal of the carriage ready to machine another work piece I I.

It will be noted that because of the construction of the upper former B,cams may be readiily applied to the recess "5 having contours to producethe desired surface in the work piece. It will be noted that it isunnecessary to remove the upper former bar B, all that has to be done isto release the screws 2'! and 28 from engagement with the cams, and easeoff the spindle bolt 32 whereupon the cams may be removed from theformer bar. Other cams may then be installed, secured by the screws 21and 2e and endwise adjusted by proper manipulation of the spindle bolt32.

In like manner, the lower cam 39, having contour faces of complementa-lshape to the contours of the cams in the upper former bar may be appliedto the recess 38 in the cradle 31 by removing the cradle from the lowerwork bar C and then moving the cam 39 from the recess in the cradle.

Alignment of the cam surfaces of the upper and lower cams may beaccomplished first by endwise adjustment of the lower cam bar C, bymoving it endwise in the bracket and tightening it in adjusted positionand a finer further adjustment of alignment by manipulation of thespindle bolt 32 against the cams in the recess B6 of the upper formerbar B. It will thus be noted that a fine adjustment may be made betweenthe cams and the apices of thecam shoes" to assure accuracy of cut ofthe workpiece.

it is to be understood that the cam arrangement of the present inventionmay also be appliedto the back-arm ofa lathe carriage.

, The springs 46 are-loaded by the bolts 41 and t3 to maintain thedesired floating pressure on the shoesiEi and and the follower cam 39 iscontoured so "that this pressure is not appreciably changed asthe shoe59 rides over the high and; low;poin tsof the cam faces 22. As a resuit,the shoes have, accurate riding engagement or =operative clearancerelation at all times with the cams without exerting excessivefrictional wear on the cams. In addition the yielding mounting for thefollower cam absorbs any changes in distance between the apices of theshoes. This invention has increased the tolerance accuracy of lathes onwhich it has been introduced from .001 inch to .0001 inch.

It will, of course, be understood that various details of constructionmay be varied through a wide range without departing from the principlesof this invention and it is, therefore, not the purpose to limit thepatent granted hereon otherwise than necessitated by the scope of theappended claims.

I claim as my invention:

1. In combination with a profile turning lathe having a rockingcarriage, a first cam mounted on the lathe alongside the path ofmovement of the carriage for controlling rocking of the carriage, afirst cam follower carried by the carriage and riding on said first cam,a second cam follower carried by the carriage, and a resiliently mountedfollower cam having a shape complementing the shape of the first cam andcoacting with said second cam follower to maintain accurate ridingcontact between thefirst follower and first cam.

2. In combination with a profile turning lathe having a rocking carriagewith a laterally extending rock arm, first and second opposed camfollowers transversely pivoted on said arm, a cam support on said lathe,a first cam carried by. said cam support and c-oacting with the firstcam follower to control rocking of the carriage, a second camcomplementary with said first cam coasting with the second cam follower,and a resiliently yieldable mounting for the second cam for maintainingaccurate riding of the first follower on the first cam.

3. In combination with a lathe having a rocking tool carriage, means forcontrolling the rocking movement of said tool carriage comprising abracket, upper and lower former bars removably mounted on the bracket,said carriage having an arm extending between said former bars, opposedcam followers pivoted on said arm, cam means in the upper former bararranged to be engaged by one of the cam followers, cam means in thelower former bar arranged to be engaged by the other of said camfollowers, and a spring mounting for the cam means in the lower formerbar to cause positive contact of the cam follower with the cam in theupper former bar without undue friction, said cam means in the lowerformer bar having surfaces complementing the surfaces of the cam meansin the upper former bar to minimize movement of the spring mounting asthe cam followers advance over the surfaces.

4. Means for controlling the rocking movement of a tool carriage in alathe comprising a bracket, former bars mounted in said bracket, a firstcam adjustably fixed in one former bar. a second cam complementary tosaid first cam and resiliently mounted in the other former bar, saidtool oarriage having an arm extending between the cams, opposed camfollower shoes pivotally mounted on the end of said arm and respectivelyhaving simultaneous line contact with the first and second 8 mentaryshape of the second cam minimizing movement of the resilient "mountingas the cam shoes advance over the cam surfaces.

' I JULIUS E. SHAFER.

' REFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name Date 23,957 Spring May 10, 18591,248,317 Groene et a1. Nov. 27, 1917 1,407,419

I-Iusted Feb. 21, 1922

